A certain type of brain cell known as an astrocyte has always been regarded as a cell analogous to a housekeeping cell in the field of neuroscience. UR researchers, however, are discovering that these cells actually perform a much more active role in influencing our brain activity at every moment.
This research is being conducted by Neurology Professor Maiken Nedergaards’s lab in the UR Medical Center (URMC). The lab’s most recent study in this area has just claimed the cover of the journal “Science Signaling” with an article entitled “Astrocytes Modulate Neural Network Activity by Ca2+-Dependent Uptake of Extracellular K+.” It is one of many that have recently been published by the Nedergaard lab in their line of research.
Nedergaard has been conducting research on astrocytes for 18 years and has been at URMC for the past eight years. The lab now has about 30 researchers, 15 of whom are undergraduates.
Their new article studies astrocytes, which have been much less investigated than neurons, primarily because of the available current technology. Until recently, basic electrical recording was the primary tool available to investigate brain activity, and, unlike neurons, astrocytes do not exhibit electrical activity measurable by this machinery.
More recently, however, brain imaging technology has developed that can show the activity of cells that do not exhibit electrical activity, such as astrocytes, which have ultimately elucidated much knowledge about these unique cells.
Astrocytes are a type of glial cell, which nourish, support and protect neurons. One way in which they accomplish this is by passively soaking up excess potassium around the neuron to restore it to its balanced chemical state. In addition to this more passive, automatic process, Nedergaard discovered that astrocytes actually regulate neuronal function actively as well.
Astrocytes lower potassium levels surrounding neurons, which in turn heightens calcium levels. These chemical fluctuations inhibit the neuron from “firing,” or passing on a message to surrounding neurons.
Although it may seem strange that an astrocyte’s key responsibility is to block neuronal signaling, inhibitory control is crucial to brain activity. Preventing certain neurons from firing is what allows our brains to focus on the information most relevant for our current tasks, like comprehending this sentence, for example, rather than focusing on the color of the ink or the curvature of the letter “e.”
If this ability is impaired, however, it can result in brain diseases such as epilepsy. Post-Traumatic Stress Disorder is a specific example in which astrocytes are widely eliminated, and although they regrow over time, they do not provide enough potassium to effectively inhibit excess neuronal activity, which unfortunately can result in epilepsy.
Therefore, Nedergaard’s research has important implications for epilepsy treatment. Most current treatments target synaptic networks, but Nedergaard explains that future medication could target astrocytes.
“[The research] opens the possibility that we are not only getting a new target, but that we are getting a much better target because astrocytes do not participate in the immediate processing of incoming input,” Nedergaard said. “This would protect the cells that are involved in important processing from the potentially harmful consequences of medical treatments.”
Nedergaard became interested in this field because of the unique properties of astrocytes. The brain possesses many more astrocytes than neurons, and they are much more complex, diverse and larger (27 times) in humans than rodents.
Scientists do not yet understand the complex mechanisms that render humans more intelligent than other animal species.
Nedergaard believes that astrocytes may be the key to this evolutionary puzzle, however.
“Perhaps it is a final processing system in our brain that is less developed in rodents,” Nedergaard said. “Astrocytes have increased tremendously during evolution, and are somehow contributing to the complex brain organization and intelligence that we have.”
Source: University of Rochester Campus News